Materials Literature
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Early stages of crystallization of polymers may be viewed as thermoreversible physical gelation in which molecular connectivity is introduced by crystallization. Effects of shear strain on the early stages of crystallization of a commercial isotactic polypropylene are studied by dynamic mechanical experiments. Shear c…
Absorption and low-frequency Raman-scattering experiments have been performed on thin films consisting of small silver clusters embedded in a porous alumina matrix. When the Raman excitation wavelength is close to the maximum (\ensuremath{\approx}420 nm) of the Mie band (dipolar surface plasmon resonance) the Raman sp…
The structure and electronic structure of amorphous ${\mathrm{WO}}_{3}$ were studied with first-principles density-functional calculations. Upon amorphization, a large increase of the band gap is observed. The empty states exhibit a tendency towards localization. We studied the filling of these states as induced by ad…
We present the results of a first principles investigation of the equilibrium properties of c-plane $\ensuremath{\alpha}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}$ surfaces. The stable structure for the $1\ifmmode\times\else\texttimes\fi{}1$ clean surface is Al terminated with a stoichiometric composition, while…
A scaling theory of local-field fluctuations and optical nonlinearities is developed for random metal-dielectric composites near a percolation threshold. The theory predicts that in the optical and infrared spectral ranges the local fields are very inhomogeneous and consist of sharp peaks representing localized surfac…
We report here a theoretical model describing specific mechanisms of heat transport in as-prepared and oxidized meso-porous silicon layers. The model is in good agreement with experimental measurements performed by micro-Raman scattering on the layers surface. For the first time, thermal conductivity inhomogeneity alo…
In order to understand the role of hole doping on electronic structure, phase stability and magnetic properties of ${\mathrm{LaCoO}}_{3}$ generalized-gradient-corrected, relativistic first-principles full-potential density functional calculations have been performed for ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Sr}}_{…
The electronic structures of the perovskite oxides $\mathrm{La}M{\mathrm{O}}_{3}(M=\mathrm{C}\mathrm{r},\mathrm{}\mathrm{M}\mathrm{n},\mathrm{}\mathrm{F}\mathrm{e},\mathrm{}\mathrm{C}\mathrm{o},\mathrm{}\mathrm{and}\mathrm{}\mathrm{Ni})$ have been studied in the local-spin density approximation $\mathrm{LSDA}+U$ metho…
We present a major improvement to the Fourier-transform infrared (FTIR) imaging technique brought about by replacement of the commonly used step-scan spectrometer with a rapid-scanning spectrometer. This advancement dramatically decreases the time required for data collection without decreasing the data quality. With…
We have investigated the conductance of carbon nanotubes under mechanical distortions likely to occur when forming nanoscale electronic devices. Using a realistic tight-binding Hamiltonian, several structure-dependent classes of electrical behavior in deformed nanotubes have been discovered. Bending, defects, and tube…
We have studied the photoassisted electron emission of single-crystal diamond (111) for photon energies from just above the diamond band gap of 5.5 eV well into the sub-band-gap regime $(h\ensuremath{\nu}\ensuremath{\approx}2.8\mathrm{eV}).$ As an independent parameter, the electron affinity was varied between -1.27 e…
We develop the theory for grazing incidence small-angle x-ray scattering (GISAXS) from nanometer-sized naked islands on a flat substrate in the framework of the distorted-wave Born approximation (DWBA). The scattered wave amplitude is composed of four terms, including all combinations of scattering from the islands an…
In our previous publication we have mistakenly claimed that the applicability of the Hellmann-Feynman theorem in fixed-node quantum Monte Carlo calculations is not subject to the manner how the nodal boundary depends on an external parameter. This statement is not correct in general, except where the Hellmann-Feynman…
The resistance R of a high-density network of 6-nm-diam Bi wires in porous Vycor glass is studied in order to observe its expected semiconductor behavior. R increases from 300 K down to 0.3 K. Below 4 K, where R varies approximately as $\mathrm{ln}(1/T),$ the order of magnitude of the resistance rise, as well as the b…
The Monte Carlo method is used to simulate electron transport for electric field strengths up to 350 kV/cm in bulk, wurtzite structure ZnO. The relevant parts of the conduction bands of a first-principles band structure are approximated by spherically symmetric, nonparabolic valleys located at the Γ and Umin symmetry…
We present first-principles approaches based on density functional theory for calculating positron states and annihilation characteristics in condensed matter. The treatment of the electron-positron correlation effects (the enhancement of the electron density at the positron with respect to mean-field density) is show…
The four-state model is proposed for description of phase transition in ferroelectric crystals of DMAGaS and DMAAlS type. Thermodynamical functions of the model are obtained in the mean field approximation. The phase transition between paraelectric and ferroelectric phases is investigated. It is established that order…
Nanofibers of a commercial styrene–butadiene–styrene triblock copolymer were electrospun from solution, and collected either as a nonwoven elastomeric fabric, or on a layer of graphite that was evaporated onto a glass microscope slide. The resulting nanofibers were elastic, birefringent, and most had diameters around…
Using the epitaxial strain, the magnetic and electronic phases can be controlled for thin films of the manganites, La 1- x Sr x MnO 3 , grown on perovskite substrates with various lattice parameters. The strain-induced orbital-ordering (disordering) via coupling with the cooperative Jahn-Teller distortion produces dif…
Effective boundary conditions, in the form of two-sided impedance boundary conditions, are formulated for the linear electrodynamics of single- and multishell carbon nanotubes (CN's). The impedance is derived using the dynamic conductivity of CN's, which is obtained for different CN's (zigzag, armchair, and chiral) in…